Shredding units, where rotating cutters are moved past a fixedly located counter-blade and the material is shredded between the rotating cutters and the counter-blade, are used for the shredding of biomaterials, for example, in agriculture or forestry, but also for the shredding of waste. Thus, DE 44 02 111 A1 describes a mobile waste shredding unit for reducing the volume of, for example, bulky waste, demolition wood, plastics materials and old tires as well as for organic waste materials, such as green cuttings, weak wood, etc. The shredding unit consists of a slow-running, cylindrical rotor, on which the cutters are mounted, and a beam-like counter-cutter arranged parallel to the rotor. The material to be shredded is fed to the shredding unit by means of a draw-in unit.
The cutters and the counter-blade are exposed to a high degree of wear are consequently replaceable. In order to obtain a long service life of the counter-blade, AT 398 509 B describes, for its use in a cutting machine, a cutting strip, the cutting edge of which is formed by two cutting surfaces (side face and top surface) which are located approximately at right angles to each other. Consequently, the side face is provided up to the cutting edge with a coating produced from a hard metal. A hard metal coating is also provided on the top surface, at a spacing from the cutting edge.
As a result of the hard metal coating, the service life of the counter-blade can be significantly increased. In this case, the gap between the cutting edge and the coating on the top surface brings about a self-sharpening effect as the softer material located in between wears more intensely whilst the cutting edge formed from hard material remains unchanged.
In the case of a hard metal, as a brittle material there is the risk of fracture when the counter-blade is stressed, for example, as a result of a material that is fed being very hard. The fracture, in this case, can run over the complete length of the counter-blade and as a result make the counter-blade unusable. However, even locally delimited outbreaks in the hard metal coating can result in the entire counter-blade having to be replaced prematurely as the desired cut size is no longer obtained overall.